A Study Of Heat Transfer Model And Experimental Validation For Exhaust Air Insulation Wall

Building energy consumption plays an important role in total national energy consumption.Reducing the heat transferred from the external walls of the building to the room can effectively reduce the air conditioning load,which is one of the important ways to promote building energy conservation.While realizing the energy saving of building exterior walls,we should also pay attention to residents' requirements for thermal comfort of indoor air environment.A novel building envelope called exhaust air insulation wall,which recovers the low-grade energy of the exhaust air to remove the heat gain/loss through the external wall,was proposed.It can reduce the temperature of the interior surface of the wall and improve indoor thermal comfort,while reducing the air conditioning energy consumption in the cooling season.Based on the existing theoretical research,heat transfer characteristics of the wall are investigated through experimental test and numerical simulation.The main contents are as follows:(1)In order to measure its heat transfer characteristics,a full-scale test cell of the exhaust air insulation wall was established.Experiments were conducted under steady-state and unsteady-state conditions.Model calculation results and experimental measurements are compared to validate the steady-state heat transfer model and the unsteady-state heat transfer model.Results show that two numerical models are both very accurate in the simulation of the thermal characteristics of the exhaust air insulation wall.In addition,the temperature of the inner surface of the wall is always very close to the temperature of the indoor air,which has advantages in maintaining the stability of indoor thermal environment and reducing the cooling load in summer.(2)The computational accuracy of the unsteady model under different discrete numbers is analyzed.The number of discrete numbers in the height direction has little influence on the calculation accuracy of the unsteady model.Therefore,the simplified one-dimensional model can achieve appropriate accuracy at the initial research stage.When it is necessary to analyze the heat transfer characteristics of the exhaust air insulation wall in detail,the two-dimensional model should be used.(3)In addition,the differences between the steady-state model and the unsteady model are discussed.The differences of interior surface temperature between steady-state model and the unsteady-state model calculations are very small.Therefore,steady-state model can be used only when the surface temperature inside the wall is precisely required,such as the energy consumption simulation of exhaust air insulation walls or simple application design.However,in places where attention is paid to the internal heat transfer characteristics of the wall,such as the analysis of internal condensation problems and detailed analysis of the heat transfer characteristics of the wall,an unsteady-state model should be used.In this paper,steady and unsteady heat transfer models for exhaust heat insulation walls are validated by experimental methods,and the thermal properties of the walls were analyzed.Above studies have shown that the wall can improve the thermal comfort of the indoor environment and save energy.The experimental results can also provide data support for further theoretical research.